[AA] Make ModRefInfo a bitmask enum (NFC) Mark ModRefInfo as a bitmask enum, which allows using normal & and | operators on it. This supersedes various functions like unionModRef() and intersectModRef(). I think this makes the code cleaner than going through helper functions... Differential Revision: https://reviews.llvm.org/D130870 GitOrigin-RevId: b128e057c191a441e3778ffc872ffca943b2e5b1